Hello Takashi, just tested it on my linux box against 4.2.0-rc8+ and there is the same 'possible recursive locking detected', but another:
[ 13.422080] ============================================= [ 13.422081] [ INFO: possible recursive locking detected ] [ 13.422082] 4.2.0-rc8+ #61 Not tainted [ 13.422083] --------------------------------------------- [ 13.422084] systemd-udevd/533 is trying to acquire lock: [ 13.422085] (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0253da3>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio] [ 13.422094] but task is already holding lock: [ 13.422094] (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0257377>] snd_usb_mixer_set_ctl_value+0xd0/0x1ad [snd_usb_audio] [ 13.422100] other info that might help us debug this: [ 13.422101] Possible unsafe locking scenario:
[ 13.422102] CPU0 [ 13.422102] ---- [ 13.422103] lock(&chip->shutdown_rwsem); [ 13.422104] lock(&chip->shutdown_rwsem); [ 13.422105] *** DEADLOCK ***
[ 13.422106] May be due to missing lock nesting notation
[ 13.422107] 4 locks held by systemd-udevd/533: [ 13.422108] #0: (&dev->mutex){......}, at: [<ffffffff813b3414>] __driver_attach+0x30/0x80 [ 13.422112] #1: (&dev->mutex){......}, at: [<ffffffff813b342c>] __driver_attach+0x48/0x80 [ 13.422115] #2: (register_mutex#4){+.+.+.}, at: [<ffffffffa0253670>] usb_audio_probe+0xa3/0x7b9 [snd_usb_audio] [ 13.422120] #3: (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0257377>] snd_usb_mixer_set_ctl_value+0xd0/0x1ad [snd_usb_audio] [ 13.422125] stack backtrace: [ 13.422127] CPU: 7 PID: 533 Comm: systemd-udevd Not tainted 4.2.0-rc8+ #61 [ 13.422128] Hardware name: Gigabyte Technology Co., Ltd. Z97X-UD5H-BK/Z97X-UD5H-BK, BIOS F6 06/17/2014 [ 13.422129] 0000000000000000 0000000071d6ca78 ffff880407bf7538 ffffffff815ba622 [ 13.422131] 0000000000000000 ffffffff8239a680 ffff880407bf75f8 ffffffff810dd54e [ 13.422133] ffff880409db64a8 ffffffff00000000 0000000182000201 ffffffff8239a680 [ 13.422135] Call Trace: [ 13.422137] [<ffffffff815ba622>] dump_stack+0x4c/0x65 [ 13.422140] [<ffffffff810dd54e>] validate_chain.isra.9+0x75d/0xf59 [ 13.422142] [<ffffffff810de69c>] ? mark_held_locks+0x5f/0x76 [ 13.422144] [<ffffffff810e0964>] __lock_acquire+0x753/0xabf [ 13.422146] [<ffffffff810e1131>] lock_acquire+0x7b/0x9c [ 13.422151] [<ffffffffa0253da3>] ? snd_usb_autoresume+0x1d/0x52 [snd_usb_audio] [ 13.422153] [<ffffffff815c4896>] down_read+0x44/0x8d [ 13.422156] [<ffffffffa0253da3>] ? snd_usb_autoresume+0x1d/0x52 [snd_usb_audio] [ 13.422160] [<ffffffffa0253da3>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio] [ 13.422162] [<ffffffff815c48d6>] ? down_read+0x84/0x8d [ 13.422167] [<ffffffffa025738c>] snd_usb_mixer_set_ctl_value+0xe5/0x1ad [snd_usb_audio] [ 13.422171] [<ffffffffa025784a>] get_min_max_with_quirks+0x155/0x5e4 [snd_usb_audio] [ 13.422176] [<ffffffffa02581c1>] build_feature_ctl+0x33a/0x419 [snd_usb_audio] [ 13.422181] [<ffffffffa02586f9>] parse_audio_unit+0x459/0xa03 [snd_usb_audio] [ 13.422186] [<ffffffffa02590f4>] snd_usb_mixer_controls+0xe8/0x169 [snd_usb_audio] [ 13.422190] [<ffffffffa02593b4>] snd_usb_create_mixer+0xb4/0x261 [snd_usb_audio] [ 13.422194] [<ffffffffa02535ba>] ? snd_usb_create_stream+0x151/0x164 [snd_usb_audio] [ 13.422197] [<ffffffffa0253ccd>] usb_audio_probe+0x700/0x7b9 [snd_usb_audio] [ 13.422199] [<ffffffff81413bb7>] usb_probe_interface+0x139/0x1c3 [ 13.422201] [<ffffffff813b329a>] driver_probe_device+0xd0/0x21a [ 13.422203] [<ffffffff813b3441>] __driver_attach+0x5d/0x80 [ 13.422205] [<ffffffff813b33e4>] ? driver_probe_device+0x21a/0x21a [ 13.422207] [<ffffffff813b1850>] bus_for_each_dev+0x77/0xa5 [ 13.422210] [<ffffffff813b2f94>] driver_attach+0x19/0x1b [ 13.422212] [<ffffffff813b2a87>] bus_add_driver+0xe8/0x1da [ 13.422213] [<ffffffff813b3a26>] driver_register+0x86/0xc3 [ 13.422215] [<ffffffff81412b6c>] usb_register_driver+0xa8/0x146 [ 13.422216] [<ffffffffa0345000>] ? 0xffffffffa0345000 [ 13.422220] [<ffffffffa034501e>] usb_audio_driver_init+0x1e/0x20 [snd_usb_audio] [ 13.422222] [<ffffffff81000380>] do_one_initcall+0x17f/0x194 [ 13.422225] [<ffffffff810c31cd>] ? __might_sleep+0x71/0x79 [ 13.422228] [<ffffffff815b96ad>] do_init_module+0x56/0x1d7 [ 13.422230] [<ffffffff81109a8b>] load_module+0x17f5/0x1c1e [ 13.422234] [<ffffffff8117994b>] ? kernel_read+0x4b/0x6d [ 13.422236] [<ffffffff8110a066>] SyS_finit_module+0x6f/0x90 [ 13.422239] [<ffffffff815c6a57>] entry_SYSCALL_64_fastpath+0x12/0x6f
Thank you.
On 08-25-15, Takashi Iwai wrote:
Could you try the patch below?
Takashi
-- 8< -- From: Takashi Iwai tiwai@suse.de Subject: [PATCH] ALSA: usb-audio: Avoid nested autoresume calls
Since snd_usb_autoresume() invokes down_read() to shutdown_rwsem, this triggers lockdep warnings like ============================================= [ INFO: possible recursive locking detected ] 4.2.0-rc8+ #61 Not tainted
pulseaudio/980 is trying to acquire lock: (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0355dac>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio] but task is already holding lock: (&chip->shutdown_rwsem){.+.+.+}, at: [<ffffffffa0355dac>] snd_usb_autoresume+0x1d/0x52 [snd_usb_audio]
One could avoid this with down_read_nested(). But a quicker solution is just to skip snd_usb_autoresume() call and relevant down_read() inside the resume path. This is already marked via chip->in_pm flag, so we can check it easily.
This patch adds the workaround in the regular resume path (via snd_usb_mixer_set_ctl_value()). A more comprehensive coverage to all resume paths will follow later.
Reported-by: Alexnader Kuleshov kuleshovmail@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de
sound/usb/mixer.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index c50790cb3f4d..dd9caac4998a 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -463,6 +463,7 @@ int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval, struct snd_usb_audio *chip = cval->head.mixer->chip; unsigned char buf[4]; int idx = 0, val_len, err, timeout = 10;
bool autoresume;
validx += cval->idx_off;
@@ -485,10 +486,16 @@ int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval, buf[1] = (value_set >> 8) & 0xff; buf[2] = (value_set >> 16) & 0xff; buf[3] = (value_set >> 24) & 0xff;
- err = snd_usb_autoresume(chip);
- if (err < 0)
return -EIO;- down_read(&chip->shutdown_rwsem);
- /* do autoresume and lock only when invoked from non-resume path */
- autoresume = !chip->in_pm;
- if (autoresume) {
err = snd_usb_autoresume(chip);if (err < 0)return -EIO;down_read(&chip->shutdown_rwsem);- }
- while (timeout-- > 0) { if (chip->shutdown) break;
@@ -506,8 +513,10 @@ int snd_usb_mixer_set_ctl_value(struct usb_mixer_elem_info *cval, err = -EINVAL;
out:
- up_read(&chip->shutdown_rwsem);
- snd_usb_autosuspend(chip);
- if (autoresume) {
up_read(&chip->shutdown_rwsem);snd_usb_autosuspend(chip);- } return err;
}
-- 2.5.0